1. Field
This disclosure relates to a negative active material, a method of preparing the same, and a lithium battery including the negative active material.
2. Description of the Related Technology
Lithium secondary batteries are used in portable electronic devices for mobile communication, such as personal digital assistants (PDAs), mobile phones, notebook computers, electric bicycles, or electric vehicles, and have twice or more the discharge voltage than conventional batteries, and may have high energy density.
Lithium secondary batteries produce electrical energy by oxidation and reduction reactions that occur when lithium ions are intercalated to or deintercalated from a positive electrode and a negative electrode, said positive electrode and negative electrode each including an active material that enables the intercalation and deintercalation of lithium ions, and having an organic electrolyte or a polymer electrolyte filled therebetween.
A positive active material, for example, an oxide that consists of lithium and a transition metal and has a structure enabling intercalation of lithium ions may be used in a lithium secondary battery. Examples of an oxide that may be used as a positive active material include, but are not limited to, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium nickel cobalt manganese oxide (Li[NiCoMn]O2, Li[Ni1-x-yCoxMy]O2).
A typical negative active material that is used in a lithium secondary battery are carbonaceous materials, such as an artificial and natural graphite or hard carbon.
Non-carbonaceous materials may have a capacity density that is 10 times greater than that of graphite. Thus, non-carbonaceous materials have been recently investigated as a negative active material for lithium secondary batteries. However, their volumetric swelling or shrinkage during charging and discharging of a lithium battery may lead to a decrease in capacity retention ratios, charging/discharging efficiency, and lifespan characteristics. Accordingly, there are limitations to using known carbonaceous and non-carbonaceous materials as high-performance negative active materials for lithium batteries. Therefore, there is a need to develop superior negative active materials for lithium batteries with improved capacity characteristics and cycle lifespan characteristics.